Last Friday, the President's Council of Advisors on Science and Technology (PCAST) released a short report outlining various steps on climate change that President Barack Obama could take during his second term. Facing political gridlock on Capitol Hill and abroad, the PCAST scientists opted to highlight steps that PCAST member Daniel Schrag, a geochemist and energy expert at Harvard University, said the president "could push for and achieve." But some scientists say that Obama's advisers should have pressed him to be more bold (see related coverage in the 22 March issue of Science).

One of the major thrusts of the report, which was discussed at PCAST's 15 March meeting in Washington, D.C., was to emphasize "climate preparedness"—a relabeling of the idea that the government should be doing more to prepare the nation to adapt to changes expected to be caused by global warming, such as rising seas, droughts, and floods. In particular, it suggested that Obama should push for new national preparedness and infrastructure renewal plans, create a national commission on climate preparedness, and support improvements to weather and climate forecasting.

The report didn't ignore the need the need to curb, or mitigate, emissions of greenhouse gases. It included options for the president to extend Environmental Protection Agency (EPA) regulations that govern carbon dioxide emissions from new power plants to existing plants, create a North American climate pact with Canada and Mexico, support carbon capture and storage (CCS), expand natural gas drilling, and expand tax credits to other renewables beyond wind.

Although PCAST called for "very substantial mitigation," its report declined to recommend the idea of putting a price on carbon pollution, a centerpiece of climate legislation that Congress rejected earlier in Obama's term-or the administration's pending decision on whether to permit the controversial Keystone XL oil pipeline from Canada. "Economy-wide, market-based solutions, such as a carbon tax or a cap-and-trade system, are excellent ways to incorporate the costs of externalities and encourage technological innovation," the report says."But given the political resistance to such approaches, there are other policy measures that can also encourage energy transformation and decarbonization."*

Those omissions have drawn fire from some climate scientists with whom ScienceInsider shared the recommendations, but also support from some environmental strategists. To give readers a flavor of the wide-ranging debate that the PCAST report has prompted, below are excerpts, which have been edited for brevity and clarity, from interviews and e-mails.

From geochemist and energy expert Ken Caldeira of the Carnegie Institution for Science in Palo Alto, California:

The president needs his "I have a dream" speech on climate and energy systems. He needs to articulate a vision of a 21st century energy system that does not use the atmosphere as a waste dump for our CO2 pollution.

Once the president has articulated the goal, he can talk about concrete steps down the path to this goal that that might be politically viable now. But, the president needs to help people keep their "eyes on the prize." Without a vision of where we are going, we will stumble before reaching our goal.

In that context, I thought there were a few disturbing uses of language in the PCAST report.

Example 1: "Mitigation is needed to avoid a degree of climate change that would be unmanageable despite efforts to adapt." (page 1)

Typically, one sees the framing as: We reduce emissions (mitigate) to allow us to avoid all the climate change we feasibly can, and then we adapt to what we cannot avoid.

This PCAST report seems to spin this around: Adaptation is inevitable, but we should reduce emissions to avoid what we cannot adapt to. (If we can adapt to a world with low-biodiversity, disproportionate damage to the poor, etc., so much the worse for them.)

Example 2: "[C]ontinue efforts to 'decarbonize' the economy. … We believe that a primary aim of new policy efforts should be to reinforce these pathways to lower CO2 emissions."

This language of "continuation" and "reinforcement" makes it seem like we already are moving in the right direction, and the main goal is simply to continue on our current path, and to reinforce what we are already doing.

Every day, we are building mountains of hardware designed to dump CO2 into the atmosphere. We need a break with past practices; we need to be moving to a mindset in which disposing of waste in the atmosphere is simply not seen as acceptable practice.

Example 3: "Support continuing expansion of shale-gas production."

Rather than articulating the need to phase out technologies that use that atmosphere as a waste dump, the PCAST report recommends the expansion of a natural gas industry whose existence depends on us allowing them to pollute our skies.

Rather than asking President Obama to articulate the message that it is no longer appropriate—to expand industries that dump CO2 pollution into the atmosphere—the PCAST report calls on him to expand such industries. How is the president going to compellingly articulate a vision of where we need to get to when at the same time he is advocating new building power plants that dump CO2 waste into the air? I fear that this is more cognitive dissonance than most citizens can bear.

University of Colorado, Boulder, policy expert Roger Pielke Jr. called the report "Overall, … pretty solid," but had the following comments on each recommendation:

1. Preparedness is a good idea, but is much broader than just "climate change" (e.g., earthquakes). I'd say that any climate policy (not "climate change" policy) should contribute to improving preparedness policy.

2. "[I]ndices of extreme events that capture these leading indicators of climate change."

This is scientifically dubious, why go there? Unnecessary for the policy arguments here.

3. "Create a National Commission on Climate Preparedness."

I am not at all convinced that such a body is needed. We have an infrastructure for disaster mitigation that has had tremendous successes over many decades (e.g., look at loss of life trends over a century). We need to support existing bodies rather than create some new top-down effort which will survey from 30,000 feet. With government downsizing efforts, we need to figure out how to support those bodies who do good work, rather than creating new bodies that will take from a shrinking pie (of both $$ and attention).

4. The slides use the phrase "climate change preparedness" almost synonymously with "disaster preparedness"—not good. The reality (at least according to current science) is that the effects of climate change on extremes won't be detected for many decades. Misleading to suggest that efforts to prepare for tomorrow's disasters equates to preparing for climate change. This is either misguided or too clever.

5. "Without very substantial mitigation, which must occur worldwide, adaptation efforts will ultimately be overwhelmed and will be extremely costly"

Adaptation may be costly, but many adaptive steps make sense irrespective of climate change and will be regardless necessary (e.g., NYC and hurricanes). Further, the ability of mitigation to limit impacts has most of its effects in the latter decades of the century and beyond. Adaptation and mitigation are simply not tradeoffs.

Adaptation overwhelmed? Not according to IPCC [the Intergovernmental Panel on Climate Change], [Nicholas] Stern, etc. That is hyperbole.

6. Energy policy stuff is all pretty boilerplate. First bullet point after the importance of mitigation is to expand shale gas—tells you something about the realpolitik.

7. New North American climate agreement

Where did that come from? Why? Because other international treaties have performed so well? ;)

From Raymond Pierrehumbert of the University of Chicago in Illinois:

I generally agree with Ken Caldeira's reactions, with some caveat that maybe PCAST was judging that a carbon price was so unlikely to pass that it would be a distraction from things Obama could actually get done.

I believe that PCAST should have emphasized the importance of implementing a price on carbon. It is not PCAST's job to do Obama's political strategizing for him. A price on carbon need not take the form of cap and trade or a carbon tax. It might be possible, for example, to impose an extraction fee ("severance payment") for coal and oil taken from federal lands. It might be possible to impose an export fee on exported coal. It might be possible to impose some kind of fee on imported tar sands oil (though that would have to be done in such a way as to not trigger problems with GATT [General Agreement on Tariffs and Trade]). It's up to the president to figure out how to make material progress with the Congress he has, but a clear statement of the magnitude of the task at hand, and its importance, should have come out of PCAST. I'm pretty much in line with what Ken Caldeira said on this.

Regarding Keystone, I myself think it is clear that Obama should say no to Keystone, because it is something in his power to do, which would have some effect on retarding development of the tar sands (despite what the flawed State Department EIS [Environmental Impact Statement] said), and because we really wouldn't get any significant benefit from saying yes; no real oil security, few permanent jobs, and most of the money goes to Canada and to refiners in free-trade zones. Turning down Keystone makes the statement that it is time to stop investing in technologies that lock us into continued fossil fuel use, and to make a bigger play on efficiency and carbon-neutral energy (including nuclear).

I'm not sure, though, that making a recommendation on Keystone is really in the purview of PCAST, since the issues are more economic and political than strictly scientific.

Ken is also right that overemphasis on natural gas is a bad thing. As his work with [Nathan] Myhrvold shows, and as Michael Levi's paper in Climatic Change also shows, natural gas may have contributed to the current pause in U.S. carbon emissions growth, but if it is a bridge, it is a short bridge of limited utility. Especially if cheap natural gas kills off renewables and next-generation nuclear.

As U.S. domestic demand for coal decreases, the pressure to expand U.S. coal exports increases. What short-term benefit we do get from the switch to natural gas would be completely lost if it results in expanded coal exports. PCAST should have recommended that the president identify policies that could inhibit coal exports, since if there is one thing that's abundantly clear, it is that most of the remaining coal needs to stay in the ground.

From Alan Robock of Rutgers University in New Brunswick, New Jersey:

I agree with Ken, and Obama needs to reject the Keystone pipeline to show that he means business. We need a renewable infrastructure, not more fossil fuel infrastructure.

From David Doniger of the Natural Resources Defense Council (NRDC) in Washington, D.C.:

The most key things I saw/heard were the "overarching importance" of carbon emission reduction (mitigation), and the strong recommendation of actions under the Clean Air Act, especially to curb CO2 emissions from new and existing power plants and methane emissions from the natural gas infrastructure.

My comment: These are the two largest steps to meet the president's target of 17% reduction in carbon pollution below 2005 levels by 2020. In fact, the target cannot be met without taking these steps.

(I would also mention the opportunity to phase-down HFCs [hydrofluorocarbons] and to replace them with low-heat-trapping refrigerants, blowing agents, etc., as well as the opportunity for a second round of carbon pollution/fuel economy standards for heavy trucks, to take them out to 2025 as has been done for cars.)

The clean energy and energy efficiency recommendations are also very important.

The idea of a North American climate agreement is also very interesting—as [PCAST member Mario] Molina emphasized, for methane leakage, for example. I note that the three countries are joint sponsors of an amendment to the Montreal Protocol to phase down HFCs globally.

Dan Lashof of NRDC calls the report a "clear-eyed vision of what we as a nation can accomplish, if our best minds put aside ideology and focus on the problem at hand."

In an interview with ScienceInsider, energy lobbyist Jeff Holmstead of Bracewell & Giuliani in Washington, D.C., said the recommendations were "a more practical look at some of the things we should be doing. … They're making recommendations within the realm of the possible."

From Robert Socolow of Princeton University:

I think the presentation of adaptation first and mitigation second may prove salutary. It may enable the restarting of the discussion (Rosina Bierbaum [a PCAST member and professor at the University of Michigan, Ann Arbor] called it the "conversation") about climate change. The current situation, where the conversation is completely muffled, is not healthy for the U.S. political process.

By beginning with adaptation, the conversation resides principally in familiar concerns, because the overlap of threats from climate threats and threats we already deal with is large. This may reduce resistance to the message that climate change is not something we should hide from. Strategies to adapt to climate change will dovetail with the current policies and practices that deal with variability and will be understood as more of the same, rather than something alien. We already have serious heat waves and droughts and storms, and there are many processes in place at every level of government to deal with them. It will be clear that, for the most part, climate change is bringing more of what we already know and suffer from. We will not need to ask exactly how much more, how quickly. We have reason to improve what we are already doing about devastation from nature's nastiness, so that many responses will be "no regrets" actions—actions that would make sense even if there were no climate change effects—such as "rebuilding smartly" (Dan Schrag's phrase). In this category, as explained by Schrag, are reforms in infrastructure, insurance, flood plain zoning, agricultural research, and water management.

Because the overlap is not perfect, the public will be educated indirectly that the threats we already know are not exactly the same as those associated with climate change. The earthquake hazard is not going to be enhanced or diminished by climate change (ignoring induced seismicity associated with the energy system and some mitigation strategies). On the other hand, sea level rise is the prime example of a consequence of climate change that has not been part of the history of adaptation, so it brings us into new territory.

I note that a continued significant effort on CCS was endorsed. I was pleased to see this. It was couched in terms of a response to the likelihood that coal will not disappear from our energy mix and will need to be dealt with as part of a full-system approach to climate change. By calling for re-energizing CCS development, PCAST is making two judgments: 1) that the coal industry is highly likely to remain competitive even as it complies with EPA restrictions on emissions of SOx, NOx, Hg, and other toxics; and 2) that a substantial price on carbon is highly likely to arrive in a time frame of relevance for a CCS development effort.

Via e-mails, a side discussion developed on the issue of whether the U.S. government should do more to regulate non-CO2 greenhouse gases, begun by Michael MacCracken of the Climate Institute in Washington, D.C.:

In my view, the most important omission related directly to science and technology aspects of the greenhouse gas issue is the failure to point out the tremendous opportunity that exists to limit warming over the next few decades by imposing strong, mandatory controls of short-lived warming agents (so methane, black carbon, and tropospheric ozone). The 2011 UNEP/WMO assessment and the related article by Shindell et al. in Science in 2012 indicate that an aggressive program to limit emissions of these substances could relatively inexpensively cut projected warming between the present and 2050 in half while also having tremendous co-benefits for health, air quality, and improved energy efficiency, in the US and around the world. Just over a year ago, Secretary of State Clinton launched an international initiative to promote this approach and it has won an increasing number of adherents, helping to build international attention and action. Yet, the approach is unfortunately not even mentioned in the PCAST recommendations (and our country really needs to step up to the plate and demonstrate leadership in this area). Carbon dioxide is not the only warming agent—we certainly have to move to limit its emissions, but we also certainly have to limit emissions of the short-lived warming agents, and doing so now needs to be a very high priority.

Pierrehumbert disagrees:

PCAST was right to leave out short lived climate pollution. Controlling short lived climate pollution has essentially zero value until we are already on a track to get CO2 emissions down to essentially zero. The UNEP reports that purport to show otherwise give a misleading impression by assuming the world ends in 2070, by failing to adequately take into account co-emittent of brown carbon (i.e. not really many strategies available to reduce soot alone), and by failing to ask the question of whether one could do better by ignoring short lived stuff for 50-100 years and putting the resources into CO2 reduction instead. PCAST seems to understand this point really well, and they were right not to distract attention from CO2.

MacCracken responds:

Ray—Well, we will just have to continue to disagree strongly on this. I am all for addressing CO2 and long-term change, but it makes no sense at all to be having continued positive radiative forcing from methane, for example, while we are waiting to get CO2 under control. The black carbon part does have some compensation so one has to prioritize going after the sources that are virtually all black carbon (so diesel engines, etc.). But allowing a warming influence to go on, whatever it is, makes no sense at all. Cutting CO2 emissions changes the warming path mostly starting in the second half of the century—the only way to do anything over the next few decades is to go after short-lived species, not instead of CO2, but in addition.

* Correction, 5:30 p.m.: It was originally reported incorrectly that the report "declined to mention" pricing carbon. The report declined to recommend this step. The sentence that refers to this has been changed and a quote from the report added.